1. Field of the Invention
The present invention relates to a reactor utilizing a crystal oscillator and a method for manufacturing the same. In particular, the present invention relates to a reactor, a micro reactor chip, and a micro reactor system for the measurement of the viscosity, density and the like of a sample and the detection of the mass of a specific substance contained in a sample as well as their manufacturing method.
2. Description of the Related Art
Active developments of small analysis systems called lab-on-a-chip have been under way in recent years. Small analysis systems of this type integrate element structures such as flow paths, reactor tanks, valves, sensors and the like on a small substrate to analyze gases and liquids flowing through these element structures. Examples of systems of this type can include biochips, which perform clinical inspection on the blood flowing through a minute flow path provided in a resin chip (Refer to Non-patent Reference 1, for example). Using such a small analysis system allows the fast analysis of a small quantity of a sample and therefore the reduction of burden on the side that provides the sample. Therefore, particularly the application of such a system to a living body is attracting attention.
Sensors utilizing various principles have been proposed for the sensor section, which is one of the components of the small analysis system. Above all, the use of QCM (Quarts Crystal Microbalance) and SAW (Surface Acoustic Waves) sensors is anticipated because these sensors are small-sized and capable of platy configuration and assumed to be easy to mount in systems.
QCM and SAW sensors utilize the oscillation of piezoelectric oscillators (particular crystal oscillators) and employ technologies for measuring the viscosity of samples that are in contact with the surface of the piezoelectric oscillator and minute mass adherent to the oscillator. More specifically, the QCM sensor oscillates at a specific frequency determined by the material properties and shape of the piezoelectric oscillator when an AC voltage is applied to electrodes formed on opposite surfaces of the piezoelectric oscillator. When a substance adheres to any electrode of the piezoelectric oscillator, the resonant frequency of the entire oscillator changes in response to mass adherent thereto. Also, the SAW sensor generates an elastic wave of a specific frequency determined by the frequency of the AC voltage, the shape of the electrode, the material properties of the piezoelectric element and the like when an AC voltage is applied to one of two pairs of blind-line electrodes thereof. The elastic wave generated is detected as a cyclic current by means of the other electrode pair due to the piezoelectric effects of the element. When a substance is then adhered between the two pairs of electrodes, the speed of the elastic wave changes in response to adherent mass. The phase, the frequency and the input/output impedance ratio also change between the voltage applied and the cyclic current detected. The technologies employed measure the mass of the substance adhered to the electrode by detecting the above-mentioned changes.
However, the detection of a specific substance is not possible with such mass measuring means. Therefore, a configuration is used which detects only a specific substance with means fixed in position for adsorbing or capturing the specific substance. As an example of such a configuration, a technique is known for using antigen-antibody reaction for protein detection (Refer to Patent Reference 1, for example. The utilization of such a configuration in a QCM or SAW sensor makes it possible to measure the minute mass of a specific substance to be measured. The utilization of the QCM or SAW sensor in the sensor section of a small analysis system therefore allows the high-precision measurement of a desired substance and the realization of an analysis system of a small-sized configuration.
The mounting of a crystal oscillator in an analysis system therefore requires a crystal oscillator to be mounted without any sample leaks. There are few disclosures and almost no specific disclosures concerning a method for mounting a crystal oscillator in a small analysis system. Consequently, such a method is analogized with typical methods for mounting a crystal oscillator as for use as a reactor. Conventional crystal oscillator mounting methods employed include methods for providing an O-ring at the interface between an analysis system base material and a crystal oscillator and pressing and contacting the oscillator and the system base material (refer to patent Reference 2, for example) and methods for bonding the base material and the oscillator (refer to Patent Reference 3, for example), and methods for gluing the base material and the oscillator.    [Patent Reference 1] JP-A-2000-338022    [Patent Reference 2] JP-A-11-14525    [Patent Reference 3] JP-T-2004-523150    [Non-Patent Reference 4] Proc. μTAS Symposium 2002, vol. 1, 187-189
However, methods that use an O-ring at the interface between the analysis system base material and the crystal oscillator require a mechanism for pressuring the crystal oscillator against the analysis system base material and have the problem that it is impossible to reduce the size of the analysis system itself. These methods also problematically require strict pressure adjustments because a small pressure on the crystal oscillator causes sample leaks between the system base material and the crystal oscillator while a large pressure on the crystal oscillator causes damage to the crystal oscillator.
Methods for gluing the analysis system base material and the crystal oscillator problematically require strict control of amounts of adhesive applied because the adhesive applied to the crystal oscillator or system base material reaches contaminates the inner walls of the flow path and reactor tank of the system and the sensing surfaces of sensors.
Methods for bonding the analysis system base material and the crystal oscillator require heat treatments at high temperatures and produce residual stresses in the crystal oscillator because of the different coefficients of thermal expansion of the crystal oscillator and the system base material after bonding. Consequently, these bonding methods problematically suffer from a drop in sensitivity of the crystal oscillator due to failure to operate at a desired frequency.
In any of the gluing and bonding methods, the fixed region of the crystal oscillator relative to the system base material is increased and the region fixed to the system base material acts as a fixed end. Oscillations reflected from the fixed region cause the crystal oscillator to oscillate in an unintended oscillation mode (spurious). Desired oscillations cannot be separated from spurious oscillations and there is also a problem of a drop in sensor sensitivity. When, on the other hand, the fixed region is reduced, a sufficient fixing strength cannot be obtained relative to the internal pressure generated from the supply of the reagent and there is also a problem of liquid leaks from the boundary between the system base material and the crystal oscillator.